Inspector Zenigata hails from Japan, city of origin unknown. According to Episode 0: First Contact, his original title was Tokyo Police Inspector whose original interest was the capture of Fujiko Mine and her then partner. His pursuit took him to New York where he met Arsene Lupin III for the first time. The master thief's cocky attitude and talents left the inspector infuriated to the point where he left the Japanese Police Force in favor of enlisting in ICPO (called Interpol in Pioneer's English dub) for the sake of specifically bringing Lupin to justice.
Zenigata has made it his life's mission to arrest Lupin. The other members of Lupin's gang are targeted for apprehension as well, but Zenigata usually ignores them when Lupin himself is present. Lupin and Zenigata appear to be the worst of enemies, but in the anime they are, in a manner of speaking, friends; something Lupin shows openly (often by greeting Zenigata with mock affection), but it is an idea Zenigata is extremely reluctant to entertain. Similarly, he is often awed by Lupin's genius, but refuses to show it. Also, when he believes Lupin to be dead, he will drop to his knees crying at the fact he couldn't arrest him before his death, and often go into isolation until someone reveals that Lupin is still very much alive. Zenigata has an attachment to Lupin with the belief that no one should kill him or worse, capture him, besides Zenigata himself. Once, when he believe Lupin was dead, he gave up his profession and became a monk (in Fuma Conspiracy). Lupin's opinion of Zenigata is a little less caring, but still filled with respect. He often seems amazed that Zenigata can keep up with him. At times he's overwhelmed by how much thought Zenigata has put into his traps for Lupin. Once, when Lupin thought Zenigata was dead, he sought to take down his supposed murderer.
While he has some interest in capturing Jigen, Goemon, and Fujiko, he is really after only Lupin. Jigen seems to have a genuine fear of being caught by Zenigata.
In The Mystery of Mamo (originally titled simply Lupin III), it is mentioned that Zenigata has a daughter named Toshiko, but this isn't developed any further. He's unable to settle down because of his eternal pursuit, and although he sometimes longs for female company he has no luck with women - in no small part due to his inability to commit himself to anything but chasing Lupin.
The anime version of Zenigata is a quite sensitive person and often cries in emotional situations, particularly when he thinks Lupin has done something out of consideration for him, or when finding out Lupin is OK after worrying about him. On occasions when Lupin appears to be dead, he mourns him more expressively than anyone else; partly from genuine grief, partly because he no longer has a goal in life. In the 1987 OVA The Fuma Conspiracy, Zenigata actually retires from police work when he believes Lupin has died and becomes a monk, believing that if he prays enough Lupin will be a law-abiding citizen in his next life. Because of this singular ambition, he is never particularly displeased when Lupin manages to escape his custody, since that means the hunt will go on. On one occasion when Zenigata is able to successfully capture Lupin and place him in prison he becomes frustrated that Lupin hasn't yet escaped after a year has passed and wishes for him to escape or be rescued by Jigen.
Zenigata even goes so far as to cryogenically freeze himself so that he can continue to chase Lupin in the future, though both his and Lupin's cryopods malfunction and they are stuck in the present.
The origin of Zenigata's and Lupin's mutual regard was based early in the series when Lupin had the chance to shoot the Inspector, but instead wished him well and escaped. Since then, an unwritten understanding between the pair has always been neither will attempt to cause the death of the other. Further, the two are best referred as unacknowledged friends; several occasions have occurred where Lupin and gang aided Zenigata out of a life-threatening situation; when a woman the Inspector loved was killed by a criminal gang, Lupin participated in avenging her murder. On another occasion when an old enemy of Lupin's shot Zenigata point blank, Lupin began a wild motorcycle chase to apprehend the killer, partly to conclude affairs with the adversary, and partly to avenge the (supposed) death of the Inspector.
(Source: Wikipedia)